Closed-circuit television (CCTV) is the use of video cameras to transmit a signal to a specific place, on a limited set of monitors. It differs from broadcast television in that the signal is not openly transmitted, though it may employ point to point (P2P), point to multipoint, or mesh wireless links. Though almost all video cameras fit this definition, the term is most often applied to those used for surveillance in areas that may need monitoring such as banks, casinos, airports, military installations, and convenience stores. Videotelephony is seldom called "CCTV" but the use of video in distance education, where it is an important tool, is often so called.[1][2]

In industrial plants, CCTV equipment may be used to observe parts of a process from a central control room, for example when the environment is not suitable for humans. CCTV systems may operate continuously or only as required to monitor a particular event. A more advanced form of CCTV, utilizing digital video recorders[3] (DVRs), provides recording for possibly many years, with a variety of quality and performance options and extra features (such as motion-detection and email alerts). More recently, decentralized IP-based CCTV cameras, some equipped with megapixel sensors, support recording directly to network-attached storage devices, or internal flash for completely stand-alone operation. Surveillance of the public using CCTV is particularly common in many areas around the world including the United Kingdom, where there are reportedly more cameras per person than in any other country in the world.[4] There and elsewhere, its increasing use has triggered a debate about security versus privacy.

In the U.S. the first commercial closed-circuit television system became available in 1949, called Vericon. Very little is known about Vericon except it was advertised as not requiring a government permit.[6]

The earliest systems required constant monitoring because there was no way to record and store the information. Recording systems would be introduced later, when primitive reel-to-reel media was used to preserve the data, where the magnetic tapes had to be changed manually. It was a time consuming, expensive and unreliable process; the operator had to manually thread the tape from the tape reel through the recorder onto an empty take-up reel. Due to these efforts, video surveillance was rare. Only when VCR technology became available in the 1970s, which made it easy to record and erase information, did video surveillance start to become much more common.[7]

CCTV recording systems are still often used at modern launch sites to record the flight of the rockets, in order to find the possible causes of malfunctions,[8][9] while larger rockets are often fitted with CCTV allowing pictures of stage separation to be transmitted back to earth by radio link.[10]

The history of CCTV in the United States varies from that of the United Kingdom. One of its first appearances was in 1973 in Times Square in New York City.[11] The NYPD installed it in order to deter crime that was occurring in the area however crime rates did not appear to drop much due to the cameras.[11] Nevertheless, during the 1980s video surveillance began to spread across the country specifically targeting public areas.[12] It was seen as a cheaper way to deter crime compared to increasing the size of the police departments.[11] Some businesses as well, especially those that were prone to theft, began to use video surveillance.[11]

During the 1990s digital multiplexing, which allowed for several cameras at once to record, and introduced time lapse and motion only recording, increased the use of CCTV across the country[12] and increased the savings of time and money. From the mid-1990s on, police departments across the country installed an increasing number of cameras in various public spaces including housing projects, schools and public parks departments.[11] Following the September 11 attacks, the use of video surveillance has become a common occurrence in the country to deter future terrorist attacks.[11]

In September 1968, Olean, New York was the first city in the United States to install video cameras along its main business street in an effort to fight crime.[13]

CCTV later became very common in banks and stores to discourage theft, by recording evidence of criminal activity. Their use further popularised the concept. The first place to use CCTV in the United Kingdom was King's Lynn, Norfolk.[14]

In recent decades, especially with general crime fears growing in the 1990s and 2000s, public space use of surveillance cameras has taken off, especially in some countries such as the United Kingdom.[citation needed]

Experiments in the UK during the 1970s and 1980s (including outdoor CCTV in Bournemouth in 1985), led to several larger trial programs later that decade.[14]

These were deemed successful in the government report "CCTV: Looking Out For You", issued by the Home Office in 1994, and paved the way for a massive increase in the number of CCTV systems installed. Today, systems cover most town and city centres, and many stations, car-parks and estates.

A more recent analysis by Northeastern University and the University of Cambridge, "Public Area CCTV and Crime Prevention: An Updated Systematic Review and Meta-Analysis," examined 44 different studies that collectively surveyed areas from the United Kingdom to U.S. cities such as Cincinnati and New York.
The analysis found that:

Surveillance systems were most effective in parking lots, where their use resulted in a 51% decrease in crime;

Public transportation areas saw a 23% decrease in crimes;

Systems in public settings were the least effective, with just a 7% decrease in crimes overall. When sorted by country, however, systems in the United Kingdom accounted for the majority of the decrease; the drop in other areas was insignificant.[15]

The results from the above 2009 "Public Area CCTV and Crime Prevention: An Updated Systematic Review and Meta-Analysis",[15][16] are somewhat controversial.[17] Earlier similar meta-analysis completed by Walsh and Farrington in 2002 showed similar results: a significant decrease in car park crime (41%), and a non-significant decrease of crime in public transit and public places.[18] This study was criticised for the inclusion of confounding variables (e.g. notification of CCTV cameras on site, improved street lighting) found in the studies analyzed (including car park studies). These factors could not be teased apart from the effect of CCTV cameras being present or absent while crimes were being committed.[16][17] Thus, a combination of factors might be important for the decrease in crime not just the CCTV cameras. The 2009 study admitted to similar problems as well as issues with the consistency of the percentage of area covered by CCTV cameras within the tested sites (e.g. car parks have more cameras per square inch than public transit).[16] There is still much research to be done to determine the effectiveness of CCTV cameras on crime prevention before any conclusions can be drawn.

There is strong anecdotal evidence that CCTV aids in detection and conviction of offenders; indeed UK police forces routinely seek CCTV recordings after crimes. Moreover CCTV has played a crucial role in tracing the movements of suspects or victims and is widely regarded by antiterrorist officers as a fundamental tool in tracking terrorist suspects. Large-scale CCTV installations have played a key part of the defences against terrorism since the 1970s. Cameras have also been installed on public transport in the hope of deterring crime,[19][20] and in mobile police surveillance vans, often with automatic number plate recognition, and a network of APNI-linked cameras is used to manage London's congestion charging zone. Even so there is political hostility to surveillance and several commentators downplay the evidence of CCTV's effectiveness, especially in the US.[21] However, most of these assertions are based on poor methodology or imperfect comparisons.[22] A more open question is whether most CCTV is cost-effective. While low-quality domestic kits are cheap the professional installation and maintenance of high definition CCTV is expensive.[23] Gill and Spring did a cost-benefit analysis of CCTV in crime prevention that showed little monetary saving with the installation of CCTV as most of the crimes prevented resulted in little monetary loss.[17] It was however noted that benefits of non-monetary value cannot be captured in a traditional cost-benefit analysis and were omitted from their study.[17] To get a full understanding of the costs and benefits of CCTV in crime prevention these factors would have to be included. A 2008 Report by UK Police Chiefs concluded that only 3% of crimes were solved by CCTV.[24] In London, a Metropolitan Police report showed that in 2008 only one crime was solved per 1000 cameras.[25] In some cases CCTV cameras have become a target of attacks themselves.[26]

Because of the bombing attempts the previous day, some of the tapes had been supposedly removed from CCTV cameras for study, and they were not functional.[28] An ongoing change to DVR-based technology may in future stop similar problems occurring.[29]

In October 2009, an "Internet Eyes" website was announced which would pay members of the public to view CCTV camera images from their homes and report any crimes they witnessed. The site aimed to add "more eyes" to cameras which might be insufficiently monitored, but civil liberties campaigners criticized the idea as "a distasteful and a worrying development".[30]

An article published in CCTV Image magazine estimates that the number of cameras in the UK is 1.85 million. The number is based on extrapolating from a comprehensive survey of public and private cameras within the Cheshire Constabulary jurisdiction.[31] This works out as an average of one camera for every 32 people in the UK, although the density of cameras varies greatly from place to place. The Cheshire report also claims that the average person on a typical day would be seen by 70 CCTV cameras.

The Cheshire figure is regarded as more dependable than a previous study by Michael McCahill and Clive Norris of UrbanEye published in 2002.[32] Based on a small sample in Putney High Street, McCahill and Norris estimated the number of surveillance cameras in private premises in London at around 500,000 and the total number of cameras in the UK at around 4,200,000. According to their estimate the UK has one camera for every 14 people. Although it has been acknowledged for several years that the methodology behind this figure is somewhat dubious,[33] it has continued to be quoted in the absence of a better figure.

The CCTV User Group estimates that there are around 1.5 million CCTV cameras in city centres, stations, airports, major retail areas and so forth. This figure does not include the smaller surveillance systems such as those that may be found in local corner shops[34] and is therefore broadly in line with the Cheshire report.

Research conducted by the Scottish Centre for Crime and Justice Research and based on a survey of all Scottish local authorities, identified that there are over 2,200 public space CCTV cameras in Scotland.[35]

Hackers and guerrilla artists have exposed the vulnerabilities of the video systems in an act dubbed "video sniffing"[36][37] They have crossed feeds, uploaded their own video feeds and used the video footage for artistic purposes.

Industrial processes that take place under conditions dangerous for humans are today often supervised by CCTV. These are mainly processes in the chemical industry, the interior of reactors or facilities for manufacture of nuclear fuel. Special cameras for some of these purposes include line-scan cameras and thermographic cameras which allow operators to measure the temperature of the processes. The usage of CCTV in such processes is sometimes required by law. [specify]

Many cities and motorway networks have extensive traffic-monitoring systems, using closed-circuit television to detect congestion and notice accidents.[38] Many of these cameras however, are owned by private companies and transmit data to drivers' GPS systems.

The UK Highways Agency has a publicly owned CCTV network of over 1,200 cameras covering the English motorway and trunk road network. These cameras are primarily used to monitor traffic conditions and are not used as speed cameras. With the addition of fixed cameras for the Active Traffic Management system, the number of cameras on the Highways Agency's CCTV network is likely to increase significantly over the next few years.[citation needed]

The London congestion charge is enforced by cameras positioned at the boundaries of and inside the congestion charge zone, which automatically read the licence plates of cars. If the driver does not pay the charge then a fine will be imposed. Similar systems are being developed as a means of locating cars reported stolen.[citation needed]

A CCTV system may be installed where an operator of a machine cannot directly observe people who may be injured by some unexpected machine operation. For example, on a subway train, CCTV cameras may allow the operator to confirm that people are clear of doors before closing them and starting the train.[citation needed]

Operators of an amusement park ride may use a CCTV system to observe that people are not endangered by starting the ride. A CCTV camera and dashboard monitor can make reversing a vehicle safer, if it allows the driver to observe objects or people not otherwise visible.[citation needed]

Some software integrates with CCTV to monitor the actions of workers in retail environments. Every action is recorded as an information block with subtitles that explain the performed operation. This helps to track the actions of workers, especially when they are making critical financial transactions, such as correcting or cancelling of a sale, withdrawing money or altering personal information.[citation needed]

Actions which an employer may wish to monitor could include[citation needed]:

Scanning of goods, selection of goods, introduction of price and quantity;

Input and output of operators in the system when entering passwords;

Deleting operations and modifying existing documents;

Implementation of certain operations, such as financial statements or operations with cash;

Moving goods, revaluation scrapping and counting;

Control in the kitchen of fast food restaurants;

Change of settings, reports and other official functions.

Each of these operations is transmitted with a description, allowing detailed monitoring of all actions of the operator. Some systems allow the user to search for a specific event by time of occurrence and text description, and perform statistical evaluation of operator behaviour. This allows the software to predict deviations from the standard workflow and record only anomalous behaviour.[citation needed]

The use of CCTV in the United States is less common, though increasing, and generally meets stronger opposition. In 1998, 3,000 CCTV systems were in use in New York City.[39] There are more than 10,000 CCTV systems in Chicago.[40]

In the last few years particularly, the percentage of people in the U.S. having installed a security-camera system has increased dramatically. Global Security Solutions with the help of Zone Tech Systems first announced the launch of IP surveillance in the U.S. security industry by partnering up with Axis Communications (an IP pioneer). Today's CCTV market has transformed the shift towards IP-based security products and systems.[citation needed]

In Latin America, the CCTV market is growing rapidly with the increase of property crime.[41]

Criminals may use surveillance cameras to monitor the public. For example, a hidden camera at an ATM can capture people's PINs as they are entered, without their knowledge. The devices are small enough not to be noticed, and are placed where they can monitor the keypad of the machine as people enter their PINs. Images may be transmitted wirelessly to the criminal.[42]

Opponents of CCTV point out the loss of privacy of the people under surveillance, and the negative impact of surveillance on civil liberties. Furthermore, they argue that CCTV displaces crime, rather than reducing it. Critics often dub CCTV as "Big Brother surveillance", a reference to George Orwell's novel Nineteen Eighty-Four, which featured a two-way telescreen in every home through which The Party would monitor the populace. Civil liberties campaign group Big Brother Watch have published several research papers into CCTV systems. In December 2009, they released a report documenting council controlled CCTV cameras.[43]

Proponents of CCTV cameras have argued that the cameras are not intruding into people's privacy, as they are not surveilling private, but public space, where an individual's right to privacy can reasonably be weighed against the intended benefits of surveillance.[44] However, both the United States Supreme Court in Katz v. United States and anti-surveillance activists have held that there is a right to privacy in public areas.[45][46] Furthermore, while it is true that there may be scenarios wherein a citizen's right to public privacy can be both reasonably and justifiably compromised, some scholars have argued that such situations are so rare as to not sufficiently warrant the frequent compromising of public privacy rights that occurs in regions with widespread CCTV surveillance. For example, in her book Setting the Watch: Privacy and the Ethics of CCTV Surveillance, Beatrice von Silva-Tarouca Larsen argues that CCTV surveillance is ethically permissible only in "certain restrictively defined situations", such as when a specific location has a "comprehensively documented and significant criminal threat" (p. 160). Her central reasoning is that widespread CCTV surveillance violates citizens' rights to privacy and anonymity within the public sphere by jeopardizing both their liberty and dignity. She concludes that CCTV surveillance should therefore be reserved for specific circumstances in which there are clear and reasonably demonstrated benefits to its implementation and few ethical compromises.[47]

Questions are also raised about illegal access to CCTV recordings. The Data Protection Act 1998 in the United Kingdom led to legal restrictions on the uses of CCTV recordings, and also mandated their registration with the Data Protection Agency. In 2004, the successor to the Data Protection Agency, the Information Commissioner's Office clarified that this required registration of all CCTV systems with the Commissioner, and prompt deletion of archived recordings. However, subsequent case law (Durant vs. FSA) has limited the scope of the protection provided by this law, and not all CCTV systems are currently regulated.[48] Private sector personnel in the UK who operate or monitor CCTV devices or systems are now considered security guards and have been made subject to state licensing.

A 2007 report by the UK's Information Commissioner's Office, highlighted the need for the public to be made more aware of the "creeping encroachment" into their civil liberties created by the growing use of surveillance apparatus. A year prior to the report Richard Thomas, the Information Commissioner, warned that Britain was "sleepwalking into a surveillance society".[citation needed]

In 2007, the UK watchdog CameraWatch claimed that the majority of CCTV cameras in the UK are operated illegally or are in breach of privacy guidelines.[citation needed] In response, the Information Commissioner's Office denied the claim adding that any reported abuses of the Data Protection Act are swiftly investigated.[49]

Today’s High-definition CCTV cameras have many computer controlled technologies that allow them to identify, track, and categorize objects in their field of view.[citation needed]

Video Content Analysis (VCA) is the capability of automatically analyzing video to detect and determine temporal events not based on a single image. As such, it can be seen as the automated equivalent of the biological visual cortex.

A system using VCA can recognize changes in the environment and even identify and compare objects in the database using size, speed, and sometimes colour. The camera’s actions can be programmed based on what it is “seeing”. For example; an alarm can be issued if an object has moved in a certain area, or if a painting is missing from a wall, or if a smoke or fire is detected, or if running people are detected, or if fallen people are detected and if someone has spray painted the lens, as well as video loss, lens cover, defocuss and other so called camera tampering events.[citation needed]

VCA analytics can also be used to detect unusual patterns in a videos environment. The system can be set to detect anomalies in a crowd of people, for instance a person moving in the opposite direction in airports where passengers are only supposed to walk in one direction out of a plane or in a subway where people are not supposed to exit through the entrances.[51]

VCA also has the ability to track people on a map by calculating their position from the images. It is then possible to link many cameras and track a person through an entire building or area. This can allow a person to be followed without having to analyze many hours of film. Currently the cameras have difficulty identifying individuals from video alone, but if connected to a key-card system, identities can be established and displayed as a tag over their heads on the video.[citation needed]

There is also a significant difference in where the VCA technology is placed, either the data is being processed within the cameras (on the edge) or by a centralized server. Both technologies have their pros and cons.[52]

Facial recognition system
Is a computer application for automatically identifying or verifying a person from a digital image or a video frame from a video source. One of the ways to do this is by comparing selected facial features from the image and a facial database.[citation needed]

Computerized monitoring of CCTV images is under development, so that a human CCTV operator does not have to endlessly look at all the screens, allowing an operator to observe many more CCTV cameras.[citation needed] These systems do not observe people directly. Instead, they track their behavior by looking for particular types of body-movement behavior, or particular types of clothing or baggage.

To many, the development of CCTV in public areas, linked to computer databases of people's pictures and identity, presents a serious breach of civil liberties. Critics fear the possibility that one would not be able to meet anonymously in a public place or drive and walk anonymously around a city.[53] Demonstrations or assemblies in public places could be affected as the state would be able to collate lists of those leading them, taking part, or even just talking with protesters in the street.

Most CCTV systems record and store digital video and images to a Digital Video Recorder or in the case of IP cameras directly to a server, either on-site or offsite.[citation needed]

The amount of data stored and the retention period of the video or pictures are subject to compression ratios, images stored per second, image size and duration of image retention before being overwritten.[54]

Recordings are usually kept for a preset amount of time and then automatically archived, overwritten or deleted. Videos are kept in order to allow retrieval and review in the event a crime was committed or the information needs to be studied for any number of reasons.[citation needed]

Closed-circuit digital photography (CCDP) is more suited for capturing and saving recorded high-resolution photographs, whereas closed-circuit television (CCTV) is more suitable for live-monitoring purposes.[citation needed]

However, an important feature of some CCTV systems is the ability to take high resolution images of the camera scene, e.g. on a time lapse or motion-detection basis. Images taken with a digital still camera often have higher resolution than those taken with some video cameras. Increasingly, low-cost high-resolution digital still cameras can also be used for CCTV purposes.[citation needed]

Images may be monitored remotely when the computer is connected to a network.[citation needed]

A growing branch in CCTV is internet protocol cameras (IP cameras). IP cameras use the Internet Protocol (IP) used by most Local Area Networks (LANs) to transmit video across data networks in digital form. IP can optionally be transmitted across the public internet, allowing users to view their cameras through any internet connection available through a computer or a 3G phone. For professional or public infrastructure security applications, IP video is restricted to within a private network or VPN,[55] or can be recorded onto a remote server.

The city of Chicago operates a networked video surveillance system which combines CCTV video feeds of government agencies with those of the private sector, installed in city buses, businesses, public schools, subway stations, housing projects etc. Even home owners are able to contribute footage. It is estimated to incorporate the video feeds of a total of 15,000 cameras.[citation needed]

The system is used by Chicago's Office of Emergency Management in case of an emergency call: it detects the caller's location and instantly displays the real-time video feed of the nearest security camera to the operator, not requiring any user intervention. While the system is far too vast to allow complete real-time monitoring, it stores the video data for later usage in order to provide possible evidence in criminal cases.[56]

The Glynn County Police Department uses a wireless mesh-networked system of portable battery-powered tripods for live megapixel video surveillance and central monitoring of tactical police situations. The systems can be used either on a stand-alone basis with secure communications to nearby police laptops, or within a larger mesh system with multiple tripods feeding video back to the command vehicle via wireless, and to police headquarters via 3G.[citation needed]

Integrated systems allow users to connect remotely from the internet and view what their cameras are viewing remotely, similar to that of IP cameras. In one incident in 2009, a lady from Boynton Beach, Florida was able to watch her house get burgled and contacted police directly from her office at work.[57]

Many consumers are turning to wireless security cameras for home surveillance.[citation needed] Wireless cameras do not require a video cable for video/audio transmission, simply a cable for power. Wireless cameras are also easy and inexpensive to install.[citation needed] Previous generations of wireless security cameras relied on analog technology; modern wireless cameras use digital technology which delivers crisper audio, sharper video, and a secure and interference-free signal.[citation needed]

Unless physically protected, CCTV cameras have been found to be vulnerable against a variety of (mostly illegal) tactics[citation needed]:

Some people will deliberately destroy cameras. Some cameras can come with dust-tight, pressurized, explosion proof, and bullet-resistant housings.

Spraying substances over the lens can make the image too blurry to be read.

Lasers can blind or damage them. However, since most lasers are monochromatic, color filters can reduce the effect of laser pointers. However, filters will also impair image quality and overall light sensitivity of cameras (see laser safety article for details on issues with filters). Also, complete protection from infrared, red, green, blue and UV lasers would require use of completely black filters[How to reference and link to summary or text], rendering the camera useless.

A digital video recorder (DVR) of closed-circuit television (CCTV) commonly has an in-built capability to export video files to an optical storage media such as digital versatile disc. In the event that the DVR is damaged, its contents cannot be easily exported. Hence, it is generally accepted that recovering video files with its timestamps from a DVR hard disk using proprietary file format in a forensically sound manner is an expensive and challenging exercise.[citation needed]